Solar Panel Efficiency Is Overrated

I tell people all the time… don’t get so wrapped up on solar panel efficiency. I get it – you want the best. The most efficient solar panel on earth sounds exactly what you are looking for. But is it in your best interest?

The current leader for panels that are commonly available in the efficiency race is likely Sunpower. I say likely because things change so quickly in the industry. But let’s just assume that is the case. Their X-Series data sheet lists a max efficiency of 21.5%. However, the more common E-Series is 20.4%. The numbers manufacturers use assume you are getting the highest module wattage in the series, which is not always currently available, or even in production yet.

We don’t sell Sunpower. Why? It’s a long story, but the short version is that we don’t feel it offers our clients the best value, or even the best panel. You have to dig deeper. Let’s look at a couple of solar modules we do offer from Mission Solar and REC.

Cost Efficiency

The Mission Solar 385W module is our go-to option. It blends a great mix of price, efficiency, and strength. The efficiency is “only” 19.11%. That is 11% lower than the Sunpower’s flagship and 6% lower than their E-Series. But when you consider price, there is no contest. The Mission Solar panel is far and away a better value in terms of the price to efficiency ratio. So if we are talking about cost-efficiency. Mission Solar wins hands-down.

We also currently offer a premium option in the REC Alpha series. They specify a 380W solar module with 21.7% efficiency. That beats Sunpower, but it’s not readily available yet here. The 360W solar module is on the shelf, and it has a 20.6% efficiency. And the price is still far lower than the nosebleed prices that Sunpower charges.

Strong Argument

Efficiency is important. Cost efficiency is also important. But what about other factors? On major comparison for Southwest Florida is wind load test results. The Sunpower option lists only a 3,000 Pascal (Pa) wind uplift rating. That is among the lowest test rating, which is typically 2,600Pa for bargain panels.

By comparison, the REC Alpha panel has a test rating of 4,000Pa, 33% higher than the Sunpower. They have passed the test for the High-Velocity Hurricane Zone (HVHZ) which is required in Miami-Dade County, the most stringent wind building code in the country. And, even better, the Mission Solar panel has a whopping 5,631Pa rating, almost double that of the Sunpower module.

In wind-prone regions, strength matters. After hurricane Irma we saw panels (installed by other contractors) sucked out of their mounts. The wind uplift strength is no laughing matter.

The Heat is On

Most people starting their research into solar panels don’t realize that heat is the enemy of solar energy production. Solar photovoltaic modules perform better at cooler temperatures. That’s why it is good to have a solar panel that handles the heat better. Panels are rated with a factor that tells us how they handle heat.

Sunpower used to be the far and away winner in this respect. But other manufacturers figured out how to improve cell and cell junction technology over the years. Now, the REC Alpha panel boasts a better temperature coefficient (-0.26% vs -0.29%). That means the REC panel will lose less performance as temperature rises. Mission Solar falls into a more standard range at -0.37%, but it’s still much better than some others. When you take into account the initial cost and the impact on lifetime energy production, Mission Solar still wins.

Many Factors

There are many other factors that come into play with selecting a solar panel. Warranties, company strength, size (relative to your roof), appearance, shade tolerance (especially half-cut panels), inverter pairing, and other factors all come together to guide us. We do the homework for you and advise you on the best value options and premium options based on your concerns and needs.

The market is constantly changing. The brands we offer will undoubtedly change in the future. I have a long list of modules that I have recommended in the past, but have been eclipsed since then.

One thing is for certain – considering efficiency in a vacuum is not in your best interest. If you are intent on getting the maximum efficiency module, wait until later this year when REC has their 21.7% efficient panel in the distribution pipeline. But by then the landscape may change. All you can do is make the best decision based on what is currently available. We are here to help you do that.





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